It is known in the automotive engine art that the provision of variable valve timing (VVT) and/or variable valve lift valve actuating mechanisms has the capability for potentially improving the system performance of an engine by reducing pump work and valve train friction, controlling engine load and internal exhaust dilution, improving charge preparation, increasing peak power and enabling the use of various transient operation control strategies not otherwise available. A myriad of VVT mechanisms have been disclosed in the prior art but the use of such mechanisms has been relatively limited. This has been due in part to their size, cost and/or operating limitations which have limited their practicality and potential value in real production engine applications.
U.S. Pat. No. 5,937,809, assigned to the assignee of the present invention, discloses variable valve timing (VVT) mechanisms which are relatively compact, and are applicable for operating individual or multiple valves. In these mechanisms, an engine valve is driven by an oscillating rocker cam that is actuated by a linkage driven by a rotary eccentric, preferably a rotary cam. The linkage is pivoted on a control member that is, in turn, pivotable about the axis of the rotary cam and angularly adjustable to vary the orientation of the rocker cam and thereby vary the valve lift and timing. The rotary cam may be carried on a camshaft. The oscillating cam is pivoted on the rotational axis of the rotary cam.